Magnetic recording disk files that utilize a transducer mounted on a slider for reading and/or writing data on at least one rotatable disk are well-known in the art. In such systems, the slider is typically attached to an actuator arm by a suspension system.
The use of laminated materials for constructing slider suspension systems in magnetic disk files is also known in the art. For example, Erpelding et al., in U.S. Pat. No. 4,996,623, issued Feb. 26, 1991, disclose a suspension system comprised of a sheet of polyimide material sandwiched between two metal layers. Similarly, Ainslie et al., in U.S. Pat. No. 4,761,699, issued Aug. 2, 1988, disclose a slider attached to a laminated suspension.
It is known that vibration of the arm and suspension in disk drives produces undesirable effects such as nonrepeatable runout of the recording element on the slider. One known approach to reducing such vibration is to incorporate a viscoelastic material into the suspension system that supports the slider. For example, Pal et al., in U.S. Pat. No. 4,760,478, issued Jul. 26, 1988, disclose a magnetic head support arm having a layer of viscoelastic material fixed to the load bearing member for damping vibrations in the support arm.
In analyzing the problem of unwanted vibrations in generalized systems, theoretical models have been developed for using a constrained layer and a constraining layer to damp the vibrations. These models indicate that the effectiveness of the overall damping obtained depends on the stiffness of the constrained layer as well as on its length. The appropriate length can be estimated in several ways, and both analytical and experimental methods have been used. For example, in a paper entitled "Damping of Flexural Waves by a Constrained Viscoelastic Layer," The Journal of the Acoustical Society of America, vol. 31 (1959), by E. M. Kerwin, the effective length of the constrained layer is related to the wavelength of bending waves.
In another paper, entitled "Length Optimization for Constrained Viscoelastic Layer Damping," The Journal of the Acoustical Society of America, vol. 48 (1970), by R. Plunkett and C. T. Lee, an effective constraining layer length is determined for single and multiple damping layers. In another paper, entitled "Viscoelasticity and Creep Recovery of Polyimide Thin Films," VLSI Memo 90-600, MIT (June 1990) by F. Maseeh and S. Senturia, the viscoelastic properties of thin polyimide films are characterized and measured.
None of the prior art discloses using the constrained layer/constraining layer principles to solve the problem of unwanted vibrations in slider suspensions for magnetic disk drives. Furthermore, as the track density of information storage media, like hard magnetic disks, increases, the need for slider suspension systems that reduce vibrations to a minimum continues to grow in importance.